1. Field of the Invention
The present invention relates to a manufacturing method for organic EL (electroluminescence) displays and to a disposing method for semiconductor elements.
2. Description of Related Art
An organic EL display which is provided with organic EL elements corresponding to pixels is anticipated to replace liquid displays in the future because the display performance is superior and thinner, lighter, more electrically efficient displays are available due to the fact that organic EL elements emit very brightly and emit spontaneously, direct current low voltage driving is possible, response is immediate, and light is emitted by a solid organic film.
In particular, an active-matrix type organic EL display using an active-matrix driving method can be adapted to multi-grading and large displays because of the high brightness and high resolution due to the fact that transistor and capacity are provided in each pixel.
An example of an active-matrix type organic EL display which has been proposed is shown in FIG. 19. This drawing shows one pixel, and a driving element, etc., which are disposed around this one pixel. In this active-matrix type organic EL display, switching transistor 34, driving transistor 37, and capacity 36 are provided for each pixel 35 made of an organic EL element. These elements are connected to a driving circuit by way of signal line 31, power supply line 32, scanning line 33, and capacity line 38. Reference numeral 19 is an electrode of pixel 35. The purpose of using plural transistors is to enhance the reliability by improving off-current, lowering the deterioration of characteristics caused by impressing a voltage on the transistor.
In this active-matrix type organic EL display, a pixel is selected by switching transistor 34, then organic EL element as a pixel 35 emits at predetermined brightness by driving transistor 37. As these transistors, use of a thin film transistor wherein an active layer is a low temperature polycrystal silicon film which can be formed on a glass base board is proposed in order to form an organic EL display on a large area of transparent base board.
Additionally, an organic EL display using the conductance control method (T. Shimoda, M. Kimura, et al., Proc. Asia Display 98, 217; M. Kimura, et al., IEEE Trans. Elec. Dev., 46, 2282 (1999); M. Kimura, et al., Proc. IDW99,171), the control of the intensity of brightness of an organic EL element is performed by changing the conductivity of electricity of a polycrystal silicon layer which forms the thin film transistor.
In an organic EL display using this method, there is a concern that the uniformity of emitted brightness is degraded due to the variability of the current supplied to the organic EL element because there is a variations in the characteristics of thin film transistor. In order to realize, for example, 256 gradations of brightness on a large area of a display by changing the current value in a thin film transistor, it is necessary to control the current value of the organic EL element within a precision of 0.5% by switching elements such as a thin film transistor. However, because the variability of the current value at the time of impressing of intermediate voltage is large in recent transistors in which the active layer is a low temperature polycrystal silicon thin film, it is therefore difficult to sufficiently control the brightness level at 256 levels.
In contrast, the variation of the characteristics of the transistors in which the active layer is a single crystal semiconductor is small; however, because such a transistor is usually manufactured in high temperature processes such as at 600xc2x0 C. or higher, it is difficult to form such a transistor on the glass base board etc. which is currently usable as a large-area transparent base board. Also, translucent, single crystal semiconductor base board such as single crystal silicon base board cannot be used as a base board for organic EL display in which display transparency is required.
Also, in an active-matrix type organic EL display in FIG. 19, the aperture ratio is as small as 10% because the light from the organic EL element as a pixel 35 is blocked by four lines of wiring 31 to 33, and 38, two transistors 34 and 37, and capacity 36. Accordingly, in order to improve the aperture ratio of the active-matrix type organic EL display, it is necessary to decrease the area of the thin film transistor or the wiring.
Furthermore, regarding enlarging the display, the area of recent amorphous silicon transistor built-in active-matrix type liquid crystal display is 1 mxc3x971 m at maximum. In an active-matrix type organic EL display, thin film transistors in which the active layer is a low temperature polycrystal silicon film is used; however, because the sizes of manufacturing devices such as vacuum devices is limited, a size such as 1 mxc3x971 m is considered to be the maximum area as it is for the liquid crystal display.
On the other hand, in an organic EL display which is provided with a thin film transistor in which an active layer is a polycrystal silicon thin film, the thin film transistor and the organic EL element are manufactured in the following ways.
First of all, the thin film transistor is formed on a glass base board 11 by a process shown in FIG. 20A to FIG. 20D.
As a manufacturing process for this thin film transistor, first of all, a film of amorphous silicon is formed on glass base board 11 by a PECVD method using SiH4 and a LPCVD method using Si2H6. Consequently, this amorphous silicon is recrystallized to form polycrystal silicon film 12 by a laser irradiating method by using an excimer laser or a solid phase growing method. FIG. 20A shows this state. Consequently, after patterning this polycrystal silicon film 12, gate insulation film 13 is formed, and gate electrode 14 is furthermore formed by film-forming and patterning. FIG. 20B shows this state.
Consequently, impurities such as phosphorus or boron are shot into the polycrystal silicon film 12 in a self-adjusting manner by using a gate electrode 14. By doing this, source drain area 15 is formed on both sides of gate electrode 14, and a CMOSFET is formed. Consequently, an insulating film 16 in the first layer is formed, and after making a contact hole on this insulating film, the source drain electrode 17 is formed by film-forming and patterning. FIG. 20C shows this state. Consequently, insulating film 18 in the second layer is formed, and after making contact hole on this insulating film, ITO electrode 19 (electrode for pixel) is formed by film-forming and patterning. FIG. 20D shows this state.
Consequently, as shown in FIG. 21A, adhesion layer 21 is formed on insulating layer 18 in the second layer, and an aperture part is formed in the pixel area on ITO electrode 19 (electrode for pixel). Consequently, layer 22 between the layers is formed on this adhesion layer 21, and an aperture part is formed on the aperture part of cohesion layer 21.
Consequently, by the plasma treatment using oxygen plasma or CF4 plasma etc., the wettability on the surface of aperture part on ITO electrode 19 (electrode for pixel) is improved. After that, positive hole injecting holes 23 which forms the organic EL element and light emitting layer 24 are formed in this aperture part. This layers are formed by a liquid phase process such as a spin coat method, a squeegee applying method, an ink jet method, or a spattering method, and a vacuum process such as a vacuum vaporization method. In Japanese Unexamined Patent Application, First Publication, No. Hei 10-12377, it is disclosed that the organic light emitting layer which is provided for emitting colors such as red, blue and green can be randomly patterned in each pixel by forming and disposing organic EL material by an ink jet method.
Consequently, as shown in FIG. 21B, after a metallic thin film is formed as cathode 25 on light emitting layer 24, and cathode 25 is sealed by a sealing agent 26. As a metal for cathode 25, metal to which a metal alkali metal or an alkaline-earth metal is added is used for the purpose of minimizing the work function. Additionally, cohesion layer 21 is arranged for the purpose of improving the cohesion between base body and layer 22 between layers, and for the purpose of obtaining the correct dimensions for the area of light emission. Also, one of the purpose for arranging layer 22 between the layers is to lower the parasitic capacity by keeping cathode 25 at a distance from gate electrode 14 and source drain electrode 17. Another purpose for arranging layer 22 between layers is to control the wettability on the surface at the time of forming positive hole injecting hole 23 and light emitting layer 24 in liquid phase process so as to achieve the correct patterning.
In this way, in the manufacturing method for a conventional organic EL display element, in order to form a transistor, the forming of a thin film over the entire display base board, and the removing of the waste part of the material which forms the thin film by patterning are repeated. In particular, the material which forms the thin film of the organic EL element part and the wiring part are removed to a great extent; therefore, there is an allowance of improvement from the viewpoint of efficient use of resources.
The present invention is achieved by focusing on the above problem in the conventional technology, and the first object of the present invention is to obtain organic EL display wherein transistors with less variation of the characteristic (transistor in which active layer is a single crystal semiconductor) is formed on a large area of a transparent base board.
A second object of the present invention is to improve the aperture ratio of the active-matrix type organic EL display.
A third object of the present invention is to reduce the amount of the material to be removed which forms the thin film in the manufacturing process of the organic EL display.
A fourth object of present invention is to achieve a method wherein an organic EL display having an area of 1 mxc3x971 m or larger is easily obtained.
In order to solve above objects, the present invention provides a manufacturing method for organic EL display characterized in having a process wherein an unit block which has a semiconductor element is disposed at a predetermined position on the display base board in the manufacturing process for an organic EL display having an organic EL element and a semiconductor element which drives this organic EL element on the base board of the display. This unit block is formed, for example, by dividing the base board such as single crystal semiconductor base board or other type of base board on which the plural semiconductor elements are formed in rows. Otherwise, a commercially available unit block can be purchased to be used.
In this method, a semiconductor element which drives an organic EL element is not directly formed on the display base board, and a unit block having this semiconductor element is disposed at a predetermined position on the base board of the display. Therefore, by using a unit block wherein a semiconductor element is formed on a single crystal semiconductor base body, a transistor in which the active layer is a single crystal semiconductor (a transistor with less variation of characteristics) can be disposed on a less heat-resistant glass base board etc. By doing this, organic EL display wherein a transistor with less variation of the characteristics is formed on a large area of a transparent base body can be obtained.
Also By doing this method, the throughput after the formation of the display is improved by inspecting the unit block which is prepared by disposing only flawless items on the display base board after eliminating defective items. By doing this, a highly reliable organic EL display can be efficiently obtained.
Also, the size of the element of the transistor in which the active layer is a single crystal semiconductor can be reduced as compared with the size of the transistor in which active layer is a low temperature polycrystal silicon thin film. By doing this, area occupied by the semiconductor element is decreased; therefore, the aperture ratio of the active-matrix type organic EL display can be improved. Also, because it is not necessary to use a large area of a base board in the manufacturing process for the unit block, the size of devices which are used in a thin film forming process or an etching process can be reduced.
Also, because a semiconductor is not formed on the display base board due to the fact that the semiconductor element is formed in the unit block, the thin film which was wastefully formed on the organic EL element and which was then removed from organic EL element for forming the semiconductor element is not formed at all. Therefore, the amount of the material removed which forms the thin film in the manufacturing process for an organic EL display can be reduced as compared to the conventional method.
In this way, the size of the manufacturing device can be reduced; therefore, the material in the manufacturing process can be conserved, and the manufacturing cost of the organic EL display can be reduced.
In the present invention, as a method for disposing a unit block at a predetermined position on the display base board, the following three methods can be selected. Also two or more of these methods can be used together.
In the first method, the concavity which accommodates to the shape of the unit block is formed at a predetermined position on the display base board, and by fitting the unit block into this concavity in the liquid, the unit block is disposed at a predetermined position on the display base board.
In the second method, a hole piercing through in the thickness direction is opened at a predetermined position on the display base board, and by increasing the pressure on one side on the display base board above the pressure on the other side, or by introducing a unit block at the position of the hole on the surface on one side of the display base board by guiding the liquid to the hole, the unit block is disposed at a predetermined position on the display base board.
In the third method, a unit block is introduced and is disposed at a predetermined position on the display base board by Coulomb attractive forces. In this case, by electrifying the predetermined position of the display base board and the unit block to have opposite electrical charges each other, or by electrifying one of the predetermined position of the display base board or the unit block, Coulomb forces are produced between the predetermined position of the display base board and the unit block.
In the method of the present invention, the material for the organic EL element should preferably be disposed by an ink jet method corresponding to the position of the pixel on the display base board. Also, the wiring which is formed on the display base board should preferably be formed by an ink jet method.
The ink jet method, as realized in the field of printing, easily disposes the liquid material at predetermined positions by increasing the movable range of the head part of the ink jet, even up to the scale of a display such as 1 mxc3x971 m for example. In contrast, in the method wherein an organic EL element and wiring are formed by patterning by film forming and etching, the size of the display which can be manufactured is limited according to the size of the necessary manufacturing device such as a vacuum device.
The method for present invention is appropriately applied to a case in which the driving method is an active-matrix method, that is, the case of an active-matrix type EL display. In the case of an active-matrix type organic EL display, each of the organic EL elements which forms a pixel are connected by wiring such as scanning lines, signal lines, and power supply lines. In this case, it is preferable that the scanning lines, signal lines and power supply lines and connecting terminals with wiring inside the unit block of these wirings be formed in advance on the display base board in the unit block, and the unit block is disposed at predetermined positions on the display base board after the connecting terminal with the wiring on the display base board is formed in advance at the position contacting these terminals at the time of disposing on the display base board. By doing this, the wiring process after disposing a unit block on the display base board can be omitted.
A unit block should preferably have plural semiconductor elements in order to drive plural neighboring organic EL elements. By doing this, because the number of unit blocks which are disposed on one organic EL display can be decreased, the cost is reduced. Also, because the number of disposing points for unit blocks is decreased, erroneous disposing of unit blocks, or wiring errors at the time of connecting the terminal of the unit block side and the terminal of the display base board side by wiring, can be reduced.
Also, by arranging the relationship of the position of plural terminals of a unit block which has plural semiconductor elements in an axisymmetric or point-symmetric, wiring errors can be reduced. As the disposing method, the following methods may be chosen.
{circle around (1)} The planar shape of the unit block is made polygonal, and plural terminals for each organic EL element are disposed so as to be rotationally symmetric centered around the center of this polygon.
{circle around (2)} The planar shape of the unit block is made equilaterally polygonal, and plural terminals for each organic EL element are disposed so as to be rotationally symmetric centered around the center of this equilateral polygon.
{circle around (3)} By the method {circle around (2)}, the rotation angle at which the terminal position does not change even if the terminal rotates is a value such as 360xc2x0 C./n (n is the number of sides of the polygon). That is, for example, in the case in which the planar shape of the unit block is a square, terminals are disposed at the same position when the rotation angle is 90xc2x0 C. In the case in which the planar shape of unit block is a pentagon, terminals are disposed at the same position when the rotation angle is 72xc2x0 C. In the case in which the planar shape of the unit block is a hexagon, terminals are disposed at the same position when the rotation angle is 60xc2x0 C.
{circle around (4)} The planar shape of the unit block is made rectangular, and plural terminals for each organic EL element are disposed so as to be axisymmetric around both center lines which are parallel with the longer sides of this rectangle and the center line which is parallel with the shorter sides of this rectangle.
{circle around (5)} The planar shape of the unit block is made rectangular, and plural terminals for each organic EL element are disposed in such a way that the terminals are disposed at the same position at the time of rotation by 180xc2x0 C. centered around the center of this rectangle.
{circle around (6)} The planar shape of the unit block is made polygonal, and plural terminals for each organic EL element are disposed along each diagonal line of this polygon, and positions of the terminals on each of the diagonal line are that the same terminal is at the same previous position after the rotation.
{circle around (7)} The planar shape of the unit block is made equilateral polygon, and plural terminals for each organic EL element are disposed along each diagonal line of this equilateral polygon, and the position of the terminals on each of the diagonal line are that the same terminal is at the same previous position after the rotation.
According to the methods {circle around (3)} and {circle around (7)}, at the time of fitting unit block into concavity which is formed on the side of the base board corresponding to the planar shape of the unit block, the position of the terminal is the same on the base board even if a side of the equilateral polygon which forms the unit block is put to any side of the equilateral polygon which forms the concavity. That is, it is not necessary to determine the corresponding side of an equilateral polygon between a unit block and a concavity in advance, and the position of the terminals always coincide when the unit block fits into the concavity.
According to the methods {circle around (4)} and {circle around (5)}, at the time of fitting a unit block into a concavity which is formed on the side of the base board corresponding to the planar shape of the unit block, the position of the terminal is the same on the base board even if the longer side and the shorter side of the rectangle which forms the unit block is put to any longer side and shorter side of rectangle which forms the concavity. That is, it is not necessary to determine the corresponding side of an equilateral polygon between a unit block and a concavity in advance, and the position of the terminals always coincides when a unit block fits into a concavity.
FIG. 22A to FIG. 22D show examples of the disposing terminals according to the method {circle around (1)} to {circle around (3)} FIG. 22E, FIG. 22F show examples of the disposing terminals according to method {circle around (4)} or method {circle around (5)} respectively. In FIG. 22E, and FIG. 22F, single dot chain line L1 is a center line which is parallel with the longer side of the rectangle, single dot chain line L2 is a center line which is parallel with the shorter side of the rectangle. FIG. 22A also shows an example of the disposing the terminals according to method {circle around (6)} or method {circle around (7)}. Additionally, in FIG. 22A to FIG. 22F, reference numeral 39 is a unit block and reference symbol T is terminal.
As a method of disposing a unit block, a method such as disposing plural groups of organic EL elements on the display base board in a manner such that neighboring red emission, blue emission, and green emission elements are one group, and disposing the unit block which has a semiconductor element for driving three organic EL elements to the position which is the center of three organic EL elements, in a manner a group-by-group, can be selected.
Also as a method of a disposing a unit block, a method such as disposing plural groups of organic EL elements on the display base board in such a manner that two red emission, two elements for blue emission, and two elements for green emission for a total six elements the neighboring organic EL, elements are in one group, and disposing a unit block which has a semiconductor element for driving six elements of organic EL element to a position which is between six elements of organic EL element, in a group-by group manner, can be selected.
According to the number xe2x80x9cnxe2x80x9d which is the number of the organic EL elements (pixels) which are driven by the semiconductor element of the unit block, the number of the unit blocks which is disposed at one organic EL display can be decreased to 1/n. Also, as the number n increases, the cost reducing effect, effect of reduced errors in disposing the unit block, and effect of decreasing wiring errors are increased.
The present invention also provides a method of disposing a semiconductor element characterized in that, in the method of disposing a semiconductor element which disposes a unit block which has a semiconductor element in a predetermined position on the base board, hole which pierces through in the thickness direction is opened in a predetermined position on the base board, unit block is introduced to the position of the hole on one side of this base board by increasing the pressure on one side of the display base board than the pressure on the other side, or by guiding the liquid to the hole.
The present invention also provides a method of disposing a semiconductor element characterized in that, in the method of disposing a semiconductor element which disposes unit block which has semiconductor element in predetermined position on the base board, unit block is drawn to a predetermined position on the base board by Coulomb attractive forces. In this case, by electrifying the predetermined position of the display base board and unit block to have opposite electrical charges, or by electrifying either one of the predetermined position of the display base board or unit block, Coulomb forces are produced between the predetermined position of the display base board and the unit block.
The present invention also provides a manufacturing method for a semiconductor device characterized in that, in a manufacturing method for a semiconductor device which has a process which disposes a unit block which has a semiconductor element at a predetermined position on the base board, wiring which is formed on the base board is formed by an ink jet method.
The present invention also provides a manufacturing method for a semiconductor device characterized in that, in a manufacturing method for a semiconductor device which has a process which disposes a unit block which has semiconductor element at a predetermined position on the base board, wiring and connecting terminals with wiring inside the unit block of this wiring are formed on the base board in advance, the unit block is disposed at a predetermined position on the base board after the connecting terminal with the wiring on the base board is formed in advance at the position where the connecting terminal contacts the terminal on the base board at the time of disposing the unit block on the base board.
The present invention also provides a manufacturing method for a semiconductor device characterized in that, in a manufacturing method for a semiconductor device which has a process which disposes a unit block which has a semiconductor element at a predetermined position on the base board, the manufacturing method for a semiconductor device is provided wherein the planar shape of unit block is made polygonal, and plural terminals for each semiconductor elements are disposed so as to be rotationally symmetric centered at the center of this polygon. In this method, the polygon should preferably be an equilateral polygon.
The present invention also provides a manufacturing method for a semiconductor device characterized in that, in a manufacturing method for a semiconductor device which has a process which disposes a unit block which has semiconductor element at a predetermined position on the base board, the manufacturing method for the semiconductor device is provided wherein a planar shape of the unit block is made rectangular, and plural terminals for each semiconductor element are disposed so as to be axisymmetric to both center lines which are parallel to the longer side of this rectangle and center line which is parallel to the shorter side of this rectangle.
The present invention also provides a manufacturing method for a semiconductor device characterized in that, in a manufacturing method for a semiconductor device which has a process which disposes a unit block which has a semiconductor element at a predetermined position on the base board, the manufacturing method of the semiconductor device is provided wherein a planar shape of a unit block is made polygonal, and plural terminals for each semiconductor element are disposed along each diagonal line of this polygon, and the position of the terminals on each of the diagonal lines are in such a way that the same terminal is at the same previous position after the rotation. In this method, the polygon should preferably be an equilateral polygon.
As a xe2x80x9csemiconductor devicexe2x80x9d in the manufacturing method for these semiconductor devices, a memory cell and a liquid crystal display can be mentioned for example. Also, the method of disposing terminals {circle around (1)} to {circle around (7)} which is explained as a manufacturing method for an organic EL display can also be applied as a method of disposing a terminal of a semiconductor element in this manufacturing method for a semiconductor device.
The present invention also provides a manufacturing method for an active-matrix type organic EL display characterized in that, in a manufacturing method for an active-matrix type organic EL display wherein a light emitting layer which is inserted among at least two electrodes per pixel and the light emitting layer is driven by a semiconductor element, is formed, a semiconductor element is formed on the base board, the semiconductor element is detached from the base board so as to be divided per unit block, the unit block of the semiconductor element is disposed on other base board.
The manufacturing method for an electro-optic device of the present invention is characterized in having process wherein a unit block having the semiconductor element is disposed at a predetermined position of the display base board in the manufacturing method for an electro-optic device which is provided with an electro-optic element and a semiconductor element which drives this electro-optic element on the display base board.
Also, an electro-optic device of the present invention is characterized in that the unit block which is provided with the driving circuit which has the semiconductor element is disposed at a predetermined position on the display base board, in the electro-optic device which is provided with an electro-optic element and a semiconductor element which drives this electro-optic element on the display base board. In addition, xe2x80x9ca driving circuitxe2x80x9d which is mentioned here includes, for example, a peripheral driving circuit which is disposed around the display region so as to produce a picture signal and scanning signal etc. for each pixel in the display region, or a transistor which drives each pixel, and wiring and terminals which are connected to the transistor.
Furthermore, plural terminals for each electro-optic element should preferably be disposed in the unit block so as to be rotationally symmetric centered around the center of the unit block in plan view.
According to the present invention, a semiconductor which drives an electro-optic element is not directly formed on the display base board, and unit block which has this semiconductor element is disposed at a predetermined position on the display base board. Therefore, by using a unit block wherein a semiconductor element is formed in single crystal semiconductor base board, transistor in which the active layer is a single crystal semiconductor (transistor with less variation of the characteristics) can be disposed on a less heat-resistant glass base board etc. By doing this, electro-optic device is obtained wherein a transistor with less variation of the characteristics is formed on a large area of transparent base board.
Also, the throughput after the formation of the display is improved by inspecting the unit block which is prepared, by disposing only perfect items on a display base board after eliminating defective items. By doing this, highly reliable electro-optic devices can be efficiently obtained.
Also, the size of the element of the transistor in which the active layer is a single crystal semiconductor can be reduced as compared with the size of the transistor in which the active layer is a low temperature polycrystal silicon thin film. Also, because it is not necessary to use a large area of base board in the manufacturing process of a unit block, the size of devices which are used in the thin film forming process or the etching process can be reduced.
Also, because the semiconductor element is not formed on the display base board due to the fact that a semiconductor element is formed in a unit block, and a thin film which would have been wastefully formed and removed to form the semiconductor element as in the conventional method is not formed at all. Therefore, the amount of the material removed for a forming thin film can be reduced in the manufacturing process for electro-optic device as compared with a conventional method. In this way, because the size of the manufacturing device can be diminished, and the materials for the manufacturing process can be conserved, the manufacturing cost of electro-optic device can be reduced.
An electronic device of the present invention is characterized in being provided with an electro-optic device of the present invention.
Effects of Invention
According to the manufacturing method for organic EL displays of the present invention, an organic EL display wherein transistors with less variation in characteristics (transistor in which the active layer is a single crystal semiconductor) is formed on a large area of the transparent base body can be obtained.
Also, according to the manufacturing method for an organic EL display of the present invention, an active-matrix type organic EL display with a high aperture ratio can be obtained.
Also, according to the manufacturing method for an organic EL display of the present invention, because the amount of the material for forming thin film which is removed in the manufacturing process for an organic EL display can be reduced, efficient use of resources and reduction in manufacturing cost can be attempted.
Also, according to the manufacturing method for an organic EL display of the present invention, by adapting the ink jet method etc., an organic EL display which is 1 mxc3x971 m or larger will soon be easily obtainable.
Also, according to the disposing method for a semiconductor element of the present invention, the disposition of a unit block against the base board can be performed more reliably and more easily than the disposing method for the unit block in the concavity of the base board.
Also, according to the disposing method for a semiconductor element of the present invention, a semiconductor device having a process wherein a unit block having a semiconductor element is disposed at a predetermined position of the base board can be easily obtained.